Transcript PP_ch21f

Local Area Networking
Chapter 21
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Overview
• In this chapter, you will learn to
– Explain network technologies
– Explain network operating systems
– Install and configure wired networks
– Install and configure wireless networks
– Troubleshoot networks
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Networking Technologies
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The Big Questions
• How will each computer be identified?
– If two or more computers want to talk at the same
time, how do you ensure all conversations are
understood?
• What kind of wire should be used?
– How many wires in the cable? How thick? How
long? What type of connectors?
• How can access to data be controlled?
• And the list goes on and on…
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A Few Basics
• A client machine requests information or
services
• Network interface card (NIC) defines the client
– Breaks data into smaller data units (packets)
• A medium to connect the devices is needed
– Wired or wireless
• Operating system needs to be network aware
• A server provides information or services to
the client
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Topology
• Bus topology
– All computers connect to the network via a
main line called a bus cable
• Ring topology
– All computers attach
to a central ring of cable
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Topology
• Star topology
– Computers on the network
connect to a central wiring
point (often a switch or a hub)
• Mesh topology
– Each computer has a
dedicated line to every
other computer
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Essentials
CompTIA A+
Essentials
Getting the Right Sound Card
Packets/Frames and NICs
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Packets, Frames, and NICs
• Data is broken up into small pieces and
moved about the network
– Data moved in chunks called packets or frames
• Every network interface card (NIC) has a
built-in identifier called a Media Access
Control (MAC) address
– Designed to be unique
– Uses 48-bit long address
– Burned into a chip
on the card
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Packet Fields
• Packets contain the following fields
– MAC address of destination NIC
– MAC address of source NIC
– Data
– Data check or cyclic
redundancy check
(CRC) used to verify
the data’s integrity
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Protocols
• Protocols are sets of rules
– May be used to define packet types, cabling and
connectors, addresses, and much more
• A hardware protocol defines how to get
data from one computer to another
– Ethernet is the dominant standard for today’s
networks
• Cables include coaxial, unshielded twisted pair, fiber optic
– Token Ring was developed by IBM but is losing
popularity
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Coaxial Ethernet
• Early Ethernet networks used coaxial
cable (or just coax)
– Composed of a center cable surrounded by
insulation, a shield of braided cable, and an outside
protective cover
– A different type of coaxial
cable is used by your VCR
and TV
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Thick Ethernet—10Base5
• Thick Ethernet cable used
– RG-8 (Radio Grade) cable
– 10Base5
• 10 means data is transferred at 10 Mbps
• 5 means the maximum length of the cable is 500 meters
– Uses a bus topology
– Computers are
connected
one to another
• Every computer
receives every
packet of
information
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CSMA/CD
• Carrier sense multiple access/collision
detection (CSMA/CD)
• To prevent collisions when there is
multiple access to a cable
– Computers first do a carrier sense (listen to the
cable for traffic) before trying to send data
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CSMA/CD
• If two computers talk (try to send data)
at the same time
– A collision results that corrupts the data
– Computers then decide when to resend the data
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Reflection and Termination
• Signals traveling along a wire will
bounce back when they get to the end
– This is called reflection
– Can corrupt signal
When an electrical signal
reaches the end of a wire…
Some of the signal
is reflected back
When an electrical signal reaches
the end of a terminated wire…
There is no reflection
• A terminator absorbs the reflection
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Connections
• Thicknet marked every
2.5 meters
– Devices are connected at
these points
– Vampire connector pierces the cable
• It is also a transceiver that transmits and receives data,
sometimes called an access unit interface (AUI) that
connects to a Digital, Intel, or Xerox (DIX) connector
• Thicknet uses a bus topology
– Break in the cable takes down the whole network
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Thicknet Connections
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Thin Ethernet—10Base2
• Thin Ethernet is
also known as
Thinnet
–
–
–
–
–
–
–
Uses RG-58 coax
Limited to 30 devices per segment
Cable length limited to 185 meters
Thinner and cheaper than Thicknet
Transceiver built into NIC
Uses twist-on BNC connectors
Uses terminators
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UTP Ethernet
• 10/100/1000BaseT (10xBaseT)
– Modern networks use UTP Ethernet
– 10BaseT runs at 10 Mbps
– 100BaseT runs at 100 Mbps
– 1000BaseT (Gigabit) runs at 1000 Mbps
– Uses a star bus topology
– Uses unshielded twisted pair (UTP) cabling
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Star Bus Topology
• Most common topology used is a star bus
– All devices are connected to a central device
• Can be a hub or a switch
– Switch makes each port a separate network
• Limits collisions
• Helps bandwidth
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Unshielded Twisted Pair
• UTP is predominant type of cabling used
– Pairs of wires are twisted together in an
unshielded cable
– UTP cables come in categories (CATs) that define
the maximum speed data can be transferred
• Called bandwidth
• CAT5, CAT5e, and CAT6 are most common today
CAT 1 Standard phone line
ISDN & T1 lines
Speeds up to 4 Mbps
CAT 3 Speeds up to 16 Mbps CAT 4 Speeds up to 20 Mbps
CAT 5 Speeds up to 100 Mbps CAT 5e Speeds up to 1 Gbps
CAT 6 Speeds up to 10 Gbps
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CAT 2
Implementing 10xBaseT
• Requires at least two pairs of wires
– One for receiving and one for sending
• Cables use RJ-45 connectors
– RJ-11 for telephones
• The Telecommunications Industry Association/
Electronics Industries Alliance (TIA/EIA) has
two standards for connecting RJ-45 connectors
– TIA/EIA 568A and TIA/EIA 568B
– Use either but be consistent
– Wires are color-coded
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1
8
Combo Cards
• Ethernet networks share same language
• Many NICs run at
10 or 100 Mbps
• Some NICs have BNC
and RJ-45 ports
• Most NICs built into
motherboards are
autosensing
– Run at speed of network
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Hubs and Switches
• Each PC is connected to a hub or switch in a
10xBaseT network
– To add a device, simply run
another cable to the hub
or switch from the device
– The maximum separation between the device and the hub
or switch is 100 meters
– Maximum of 1024 PCs per hub or switch
– Hubs act as repeaters that
regenerate the signal before
they send it back out to other ports
– Hubs come in 4, 8, 16, or 24 ports
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Duplex and Half-Duplex
• Modern NICs can both send and receive
data at the same time
– Called full duplex
• Older NICs could send and receive data
but not at the same time
– Called half duplex
– Similar to a walkie-talkie
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Fiber Optic Ethernet
• Uses light instead of electricity
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–
–
–
–
Immune to electrical interference
Signals can travel up to 2000 meters
Most Ethernet uses 62.5/125 multimode cable
Uses two cables
Uses SC (square-shaped) or ST (round) connectors
Common standards
• 10BaseFL and 100BaseFL
– Usually reserved for data
centers due to expense
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Token Ring
• Developed by IBM
• Uses a star ring topology
– Incompatible with Ethernet
– Data travels in a ring
• Uses token passing
– A free token circulates the ring
– A device may send data only
when it has the token
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Implementing Token Ring
• Legacy Token Ring ran at 4 Mbps or 16 Mbps
using IBM Type 1 cable
– Two-pair, shielded twisted pair
(STP) cable
– Today’s Token Ring networks
may use UTP or STP
– STP comes in various types
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Token Ring Connectors
• Token Ring cables use an IBM-type Data
Connector (IDC)
– Universal Data Connectors (UDC) designed to plug into
each other
– Uses a special hub called a
multistation access unit
(MSAU or MAU)
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Other Connections
• Can connect two PCs together
– Parallel/serial
• Using crossover IEEE 1284 cable for parallel ports
• Use an RS-232 cable for serial ports
– FireWire
• Network aware
• Just connect
– USB
• Not quite as easy as FireWire but possible
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IT Technician
CompTIA A+
Technician
Network Operating System
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Client/Server
• In a client/server environment, one
machine is dedicated as a resource
– Shared over the network
– Uses a special network operating system (NOS)
• Optimized for sharing files and printers or other resources
• Protects access to the data or resources using security
– Called the server
– All other machines are clients or workstations
– Novell NetWare is an enterprise-level NOS
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Peer-to-Peer
• In a peer-to-peer network, any machine
on the network can act as client or server
• Peer-to-peer network operating systems
include
–
–
–
–
–
–
Windows 2000/XP
Limited to 10 users accessing a file at one time
Microsoft recommends no more than 15 PCs
Useful for small networks only
Limited security
Also referred to as a workgroup
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Peer-to-Peer
• User must log on to each individual
computer
– Multiple computers, multiple logons
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Domain-Based
• User logs onto domain controller
– One user, one logon
– Can access all computers (unless locked down
with security)
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Domain-Based
• Servers on the network may play one or
several roles
–
–
–
–
–
Domain controller (holds the security database)
File server
Print server
Fax server
Remote access services
(RAS) server
– Application server
– Web server
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Administrator Account
• Special user account that has complete
and absolute power over entire system
• Password should be protected
• Joining a workgroup or becoming part of
a domain is relatively easy
– Need Administrator access
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Joining a Workgroup or Domain
in Windows 98
• Joining a workgroup or becoming part of
a domain is relatively easy
– Need Administrator access
– Select computer properties
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Protocols
• Network protocol software
–
–
–
–
Takes incoming data received by the network card
Keeps it organized
Sends it to the application that needs it
Takes outgoing data from application and hands it
over to the NIC to be sent out over the network
• The most common protocols used are
–
–
–
–
NetBEUI—nonroutable, rarely used today
IPX/SPX—used by Novell
TCP/IP—used on Internet and most networks
AppleTalk—proprietary Apple protocol
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Client and Server Software
• Client software
– Needed to access data and resources on a network
– Windows installs Client for Microsoft Networks
• Server software
– Any Windows PC may be turned
into a server by enabling sharing
of files, folders, and printers
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Installing and Configuring
a Wired Network
`
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`
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Network Connectivity
• To connect to a network you need
– Network interface card
• Physical hardware that connects the PC to the network wire
– Protocol
• The language the devices use to communicate
– Network client
• Allows the computer system to speak to the protocol
– To share resources, enable Microsoft’s File and
Print Sharing
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Installing a NIC
• When choosing a NIC, there are three
requirements
– Must run at the proper speed (many NICs run at
more than one speed)
– Must be for the proper technology
• Ethernet, Token Ring, fiber optic (FDDI)
– Must fit into your expansion slot
• PCI
• If NIC does not autoinstall, then use the
Add Hardware Wizard in Control Panel
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Configuring a Network Client
• You need a network client for each type
of server NOS
– Client for Microsoft Networks
• Right-click My Network Places (or Network Neighborhood)
and choose Properties
• Double-click the Local Area Connection icon (or choose
Create a New Network Connection) and select Properties
• Client for Microsoft Networks is automatically installed
when you install a NIC in Windows
– Client Service for NetWare
• Provides access to file and print services on NetWare
servers
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Client for Microsoft Networks
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NetBEUI in Windows 2000
• NetBEUI
– Windows 2000: Start  Settings  Network and
Dial-up Connections  Double-click the Local Area
Connection icon
– Click the Properties button
– Click Install button, highlight
Protocols, and click
Add  NetBEUI
– Windows XP has dropped
support for NetBEUI
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NetBEUI
• NetBEUI
– Not routable (can’t go through routers)
– Rarely used today
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NWLink
• Microsoft’s implementation of IPX/SPX
– You’ll also need to install Client Services for
NetWare
– Install the same way you install NetBEUI but
choose NWLink instead
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Configuring TCP/IP
• TCP/IP is the most widely used protocol
suite in networks today
– It is the protocol of choice for the Internet but is
also used on private networks
– TCP/IP is installed just like NetBEUI and NWLink—
simply choose Internet Protocol (TCP/IP)
– You’ll need to configure an IP address and a subnet
mask at the very least
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IP Addressing
• IP addresses are unique on a network
• Expressed in dotted-decimal notation
– 202.34.16.11
• Composed of 32 bits in four octets
–
–
–
–
202 expressed as
34 expressed as
16 expressed as
11 expressed as
1
0
0
0
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1
0
0
0
0
1
0
0
0
0
0
0
1
0
1
1
0
0
0
0
1
1
0
1
0
0
0
1
IP Addressing
• IP addresses are broken into classes
based on the size of the network
– First number in dotted-decimal format
determines class
• 15.16.17.18 15 is Class A
• 192.7.8.9
192 is Class C
– First number also determines subnet mask
Class
Class A
Class B
Address Range
1–126
128–191
Subnet Mask
255.0.0.0
255.255.0.0
Class C
192–223
255.255.255.0
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Classes of IP Addresses
• Some addresses are reserved
– 127.0.0.1 (the loopback address) is reserved
for testing
– Three ranges are reserved for private networks
• 10.0.0.1 thru 10.255.255.255.254
• 172.16.0.1 thru 172.31.255.254
• 192.168.0.0 thru 192.168.255.254
– One range is reserved for Automatic Private IP
Addressing
• 169.254.0.1 thru 169.254.255.254
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Subnet Mask
• The subnet mask defines which portion
of the IP address belongs to the network
ID and which part belongs to the host ID
– Expressed as dotted-decimal format as 32-bit
number starting with 1s and ending with 0s
– 1s represent a network-ID bit and 0s represent a
host-ID bit
• For example, 11111111.00000000.00000000.0000000
means that the first 8 bits define the network ID and the
last 24 bits define the host ID
– The subnet mask is associated with an IP address
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IP Addresses
• Two parts of an IP address
– Network ID represents the network or subnet
– Host ID represents the individual device
• You determine which is which with the
subnet mask
– When the subnet mask is maximum, that portion of
the IP address is the network ID
192.168.1.15
255.255.255.0
192.168.1.0
10.15.16.17
255.0.0.0
10.0.0.0
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IP address
Subnet Mask
Network ID
TCP/IP Services
• TCP/IP is an entire suite of protocols
that offers TCP/IP services such as
– Hypertext Transfer Protocol (HTTP) used on the
World Wide Web
– Telnet used to access remote systems
– Ping to check communication
• TCP/IP is used to link multiple networks
(local area networks or LANs) with
other networks
– Forms a wide area network (WAN)
– Routers are used to route traffic among the LANs
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Typical LAN
• Shows two networks or subnets
– Router is path to other network
• This router has two NICs (one on each network)
• Data sent from CPU1 to CPU2 goes through Default
Gateway (different subnet)
Subnet 2
Network ID 192.168.15.0
255.255.255.0
Subnet 1
Network ID 192.168.1.0
255.255.255.0
CPU2
CPU1
`
`
`
`
Router
`
Default
gateway
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Default
gateway
`
TCP/IP Settings
• Domain name service (DNS)
– To reach any host on a TCP/IP network, you need
to know the IP address
– Instead of remembering IP addresses, you most
likely simply remember a user-friendly name
– DNS resolves user-friendly
names to actual IP addresses
(name resolution)
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Name Resolution
• Two types of names
– Internet (host) and Windows (NetBIOS)
• Seven types of name resolution
– Focus here only on DNS and WINS
Name Type
Host
Internet name
Static
HOSTS
file
Dynamic
DNS
server
NetBIOS
LMHosts WINS
server
Windows name file
Broadcast
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Cache
Hosts cache
View with
IPConfig /DisplayDNS
NetBIOS cache
View with NBTSTAT –C
TCP/IP Settings
• Windows Internet Name Service (WINS)
– Enables Windows network names to be resolved to
IP addresses (like DNS does for Internet names)
– When configuring a NIC, you
would define the IP address
of the WINS server
– WINS is being used less
and less
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TCP/IP Settings
• IP address
• Subnet mask
• Default gateway
– The address of a
machine (usually a
router) that will deliver
messages to hosts
outside of your local
segment or subnet
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TCP/IP Settings: DHCP
• Dynamic host configuration protocol
– Can manually configure
TCP/IP settings
– Can configure to get TCP/IP
settings automatically
(from DHCP)
– Requires DHCP server
– On the client computer, simply
choose Obtain an IP
Automatically
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address
TCP/IP Tools: Ping
• Ping
– Tests connectivity to a remote host
– Many options use ping /? for help
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TCP/IP Tools: IPCONFIG
• IPCONFIG
– Displays your TCP/IP settings in Windows
NT/2000/XP
– Release and Renew allows you to get new TCP/IP
information from a DHCP server
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TCP/IP Tools: NSLOOKUP
• NSLOOKUP
– Determines the name of a DNS server among
other things
• Type exit to return to the command prompt
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TCP/IP Tools: TRACERT
• TRACERT
– Shows the route a packet takes to its destination
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TCP/IP Tools: APIPA
• Automatic Private IP Addressing (APIPA)
– If set to get addresses from DHCP but DHCP server
cannot be reached, APIPA address is assigned
• Automatically assigns an IP address in range 169.254.0.0
thru 169.254.255.254 with a subnet mask of 255.255.0.0
• No routing capabilities
DHCP can’t be reached
APIPA address assigned
`
DHCP
`
`
CPU1
Router
`
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`
Sharing Drives and Folders
• To share a drive or folder, right-click it
and select Sharing
– Share name is the name others
will see on the network
– Windows 2000/XP uses
NTFS-formatted drives
• Allows for much greater and precise control
• Set the network (Sharing tab) permissions to Full Control
• Then use NTFS permissions (Security tab) to exercise more
precise control over who accesses the shared resource and
how they access them
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Sharing Drives and Folders
• Share Permissions
–
–
–
–
Full Control
Change
Read
NTFS Permissions
allow more control
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Accessing Shared Resources
• Access shared drives or folders using My
Network Places (Windows 2000/XP)
– You may also map a drive letter to a shared drive
or folder
– Windows 2000 allows you to add a network icon
instead of using a drive letter
– Windows XP adds a menu option
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UNC
• Universal Naming Convention (UNC)
– Allows you to access network resources as follows
\\SERVER1\FREDC
Computer name
Share name
– Can enter directly from Run line to access UNC
path
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Sharing Printers
• To share a printer, just right-click on the
printer and choose Sharing
• To access the printer
– Use the Add Printer icon
– Select Network Printer
instead of Local Printer
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Essentials
CompTIA A+
Essentials
Getting the Right Sound Card
Installing and Configuring
a Wireless Network
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Introduction
• Wireless networks are growing in
popularity
• Wireless networks use radio waves or
beams of infrared light to communicate
with each other
• Two primary types of wireless networks
– Based on IEEE 802.11 standard
– Based on Bluetooth technology
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Wireless Networking Components
• Many capabilities built-in today
– Infrared ports standard in laptops, PDAs, and highend printers
– Infrared not usually included in desktop PCs
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Wireless Networking Components
• Wireless Ethernet and Bluetooth often
integrated or can easily be added
– USB, PCI, PCI Express, or PC Card adapters
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Wireless Networking Components
• Wireless access point (WAP)
– Acts like a hub to the wireless hosts in the area
• Bluetooth
– Built-in option on many
newer PCs
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IT Technician
CompTIA A+
Technician
Wireless Networking Software
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Wireless Networking Software
• Wireless devices use same networking
clients and protocol as wired networks
– Use CSMA/CA (CA stands for collision avoidance)
• Another option is using Request to Send/Clear to Send
(RTS/CTS)
• Sending node issues an RTS to the receiving node as
a request
• Receiving node replies with a CTS when it’s clear
• Once data is received, receiving node sends an ACK
(acknowledge)
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Wireless Configuration Utility
• Wireless networking software is PnP
– Use a utility to configure parameters
• Windows built-in utility or vendor provided
• Configure the Service Set Identifier (SSID) here
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Wireless Networking Modes
• Ad-hoc mode
– Each wireless node is in direct
contact with every other node in a
decentralized free-for-all
– Form an Independent Basic
Service Set (IBSS)
– Called peer-to-peer mode
– Good for a few computers or
temporary network such as study
groups or business meetings
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Wireless Networking Modes
• Infrastructure Mode
– Use one or more WAPs to
connect wireless nodes to a
wired network segment
– A single WAP is called a Basic
Service Set (BSS)
– Additional WAPs create an
Extended Basic Service Set
(EBSS)
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Wireless Networking Security
• Three methods used to enhance security
1. Service Set Identifier (SSID)
– Configure a unique SSID or network name
• Default is often name of vendor such as “LinkSys”
• Widely known so easy to guess
– Each node needs to have the same SSID
– Turn off SSID broadcasting
2. MAC filtering
– Filtering based on each host’s MAC address
– Creates a type of accepted user
– Included in each packet, so can be discovered
and impersonated
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Wireless Networking Security
• Wireless Equivalency Privacy (WEP)
– Encrypts data using 40-bit or 104-bit encryption
– Provides authentication based on MAC addresses
– Significant flaws
• Wi-Fi Protected Access (WPA)
– Interim upgrade to WEP
– Uses encryption key integrity-checking
• WPA2 (IEEE 802.11i )
– Full upgrade to WEP
– Significant improvements
– Current wireless security standard
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Speed and Range Issues
• Wireless speeds range from 2 Mbps to
54 Mbps
• Speed affected by range
– Speed dynamically negotiated
– Maximum throughput at approximately 25 feet
– At edge of range, throughput may decrease to
1 Mbps
– Range not exact
• Often listed as around 150 feet or 300 feet
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Wireless Networking Standards
• 802.11-based wireless networking
– Three primary standards
– All can work in ad-hoc or infrastructure modes
Max
throughput
Max range
Frequency
Security
Compatibility
802.11a
54 Mbps
802.11b
11 Mbps
802.11g
54 Mbps
150 feet
5 GHz
SSID, MAC,
WEP, WPA
802.11a
300 feet
2.4 Ghz
SSID, MAC,
WEP, WPA
802.11b
300 feet
2.4 Ghz
SSID, MAC,
WEP, WPA
802.11b, 802.11g
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Wireless Networking Standards
• Infrared wireless networking
– Simple way to share data without adding any additional
hardware or software
– Uses the Infrared Data Association (IrDA) protocol
– Line-of-sight required
– No authentication or encryption
• You can’t be more than 1 meter away
Max throughput
Max range
Security
Compatibility
Communication mode
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Infrared (IrDA)
Up to 4 Mbps
1 meter (39 inches)
None
IrDA
Point-to-point ad-hoc
Wireless Networking Standards
• Bluetooth
– Designed to create small wireless personal area
networks (PANs)
– Typically used for peripherals
• Mice, keyboards, PDAs, etc.
Max throughput
Max range
Compatibility
Communication
mode
Bluetooth
1 Mbps
10 meters
Bluetooth
PAN
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
High-powered Bluetooth
2 Mbps
300 feet
Bluetooth
PAN
Wireless Networking Standards
• Cellular
– Many PDAs and phones today allow connection to
Internet
– Downloads as quick
as 400 to 700 Kbps
– Cellular networks have
their own protocols
– Downside is the price
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Configuring Wireless Networks
• Physically installing a wireless NIC is the
same as installing a wired NIC
• Wireless network configuration utility
– Used to configure additional
parameters
– Configure SSID and encryption
– Configure communication mode
• Ad-hoc
• Infrastructure
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Configuring Wireless Networks
• Wi-Fi
– Ad hoc
• Each wireless node needs to be configured with the same
network name (SSID)
• May need to select a common channel
• Configure unique host IP addresses
• Configure File and Printer Sharing
– Infrastructure modes
• Requires a wireless access point (WAP)
• All nodes need to be configured with the same SSID
• Configure the WAP with clients that match the chosen
options
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Configuring Wireless Networks
NETGEAR
wireless
configuration
utility
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Configuring Wireless Networks
• Configuring a wireless access point is
often done through a Web browser
– Enter the WAP’s default IP address (see your
documentation or try 192.168.1.1) in your browser
– Enter the default administrative password (in your
documentation) to log in
• The next few slides show some screenshots of the
configuration pages
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Configuring Wireless Networks
• Sample home page
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Configuring Wireless Networks
• Configuring MAC
address filtering
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Configuring Wireless Networks
• Configuring encryption
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Configuring Wireless Networks
• Infrared
– Not much to configure
– Confirm the IrDA protocol
is installed
– To transfer files
• Use Wireless Link applet
• Use Windows Explorer
– To network two computers
• Choose Connect Directly to
Another Computer
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Configuring Wireless Networks
• Bluetooth
– Completely plug and play
• May need to use vendor-supplied drivers
– Bluetooth devices seek each
other out
• Establish a master/slave relationship
– PANs sometimes have
specialized software utility
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Troubleshooting Networks
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Troubleshooting Networks
• Networked and non-networked situations
differ drastically
– Networked situations add complexity
If a user can’t print from CPU1, it could be due to
many possible problems on the network.
Print
server
`
`
CPU1
`
Router
or switch
`
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Networked
printer
Troubleshooting Networks
1. Verify the symptom
– Talk with the user to try to get a precise
description of the symptoms
2. When did it happen?
– Does it happen during boot, when the OS loads, or
after the system has been running for a while?
3. What has changed?
– Try to find out if anything has changed
– Even recent changes before the problem
began occurring
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Troubleshooting Networks
4. Check the environment
– Heat, humidity, dirt
– What OS? What applications? Do others use
the computer?
5. Reproduce the problem
– If a problem happens only once, it’s not a problem
– Otherwise, try to make the problem happen again
6. Isolate the symptom
– Hardware—remove suspect parts
– Software—remove background programs or boot
into Safe Mode
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Troubleshooting Networks
7. Separate hardware from software
– Replace the suspect hardware with known
good hardware
– Uninstall the suspect software and reinstall it
– Install the latest patch or upgrade
– Check for viruses
8. Research
– Use search engines on the Internet
9. Make the fix and test
– Keep track of what you did so you may return to
the previous state if the fix does not work
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
OSI Seven-Layer Model
• Use as a guide in
troubleshooting
Layer Number
Layer 1: Please
Name
Physical
Layer 2: Do
Data Link
Layer 3: Not
Layer 4: Throw
the
Layer 5: Sausage
Network
Transport
Description
NICs (link light), cables,
switches, hubs, etc. 1s, 0s
MAC addresses and
CSMA/CD
IP operates here
TCP/UDP operate here
Session
Manages connections
Layer 6: Pizza
Layer 7: Away
Presentation Describes how to present data
Application
Interacts with user
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
Mike’s Four-Layer Model
• Hardware
– Check the hardware starting with the physical layer
• Protocols
– Is it installed and configured properly?
• Network
– Servers and nonservers
– Check users and groups and share names
• Shared resources
– Make sure the resource has been properly shared
– Check the access allowed
© 2007 The McGraw-Hill Companies, Inc. All rights reserved
© 2007 The McGraw-Hill Companies, Inc. All rights reserved